Dental calculus, or tartar as it is sometimes called, is a deposit which forms on the surfaces of the teeth at the gingival margin. Supragingival calculus appears principally in the areas near the orifices of the salivary ducts; e.g., on the lingual surfaces of the lower anterior teeth and on the buccal surfaces of the upper first and second molars, and on the distal surfaces of the posterior molars.
Mature calculus consists of an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to bone, enamel and dentine. An organic portion is also present and consists of desquamated epithelial cells, leukocytes, salivary sediment, food debris and various types of microorganisms.
As the mature calculus develops, it becomes visibly white or yellowish in color unless stained or discolored by some extraneous agent. This is undesirable from an aesthetic standpoint.
A wide variety of chemical and biological agents have been suggested in the art to retard calculus formation or to remove calculus after it is formed. Mechanical removal of this material periodically by the dentist is, of course, routine dental office procedure.
The chemical approach to calculus inhibition generally involves chelation of calcium ion and/or crystal growth inhibition which prevents the calculus from forming and/or breaks down mature calculus by removing calcium.
The prior art discloses a number of chelating agents for this purpose. British Patent No. 490,384, Feb. 15, 1937, discloses oral compositions containing ethylenediaminetetraacetic acid, nitrilotriacetic acid and related compounds as anticalculus agents. U.S. Pat. No. 3,678,154, July 18, 1972 to Widder et al. discloses oral compositions containing certain polyphosphonates and fluoride. U.S. Pat. No. 3,737,533, June 5, 1973 to Francis discloses oral compositions containing certain carbonyl diphosphonates.
In addition to the above references, the prior art discloses dentifrices and mouthwashes containing soluble pyrophosphate salts which have been included for a variety of purposes, some for providing an anticalculus benefit. Included among such references are U.S. Pat. No. 2,941,926, June 21, 1960 to Salzmann et al. which discloses dental powders containing chlorophyll and pyrophosphate salts. U.S. Pat. No. 3,137,632, June 16, 1964 to Schiraldi discloses toothpastes containing pyrophosphate salts. U.S. Pat. Nos. 3,927,201 and 202, Dec. 16, 1975 to Baines et al. and Harvey et al., respectively, disclose toothpastes which utilize soluble pyrophosphates as abrasives. U.S. Pat. Nos. 4,244,931, Jan. 13, 1981 and 4,247,526, Jan. 27, 1981 to Jarvis et al. disclose pyrophosphate salts in dicalcium phosphate systems. Jap. Patent Application Disclosure No. 4945-1974 discloses soluble pyrophosphates in a variety of dentifrice systems. U.S. Pat. No. 4,333,551, Apr. 6, 1982 to Parran discloses tetraalkali metal salts in mouthwash compositions. U.S. Pat. No. 4,515,772, May 7, 1985 to Parran, et al., discloses compositions containing soluble pyrophosphate salts as anticalculus agents. Parran et al. achieve soluble pyrophosphate systems through the use of acid pyrophosphate salts.
In addition to the use of the above mentioned materials the use of certain acrylic acid polymers and other agents have also been disclosed for use as anticalculus agents. Included among such agents are polyelectrolytes such as copolymers of maleic anhydride and ethylene disclosed in U.S. Pat. No. 3,429,963, Feb. 25, 1969 to Shedlovsky. Shedlovsky also discloses polyacrylic acid having an average molecular weight of 1500 and greater. Another reference disclosing polyacrylic acids in oral compositions is South African Patent No. 720,898, Sept. 12, 1972 which discloses such acids having a molecular weight in the range of 2,000 to 4,000,000 for use as a membrane to prevent the elution from teeth of previously applied agents. U.S. Pat. No. 3,956,480, May 11, 1976 to Gaffar discloses complexes of anionic polymers (e.g. acrylic acid) and a cationic therapeutic agent (e.g., chlorhexidine) as anticalculus agents. Strontium chelates have also been disclosed for use in oral compositions, particularly in the enhancement of fluoride uptake.
The effect of a strontium-EDTA complex in combination with sodium ricinoleate and a fluoride source is found in the Journal of Dental Research (1982) 61 (3) 451-455. The combined effect of strontium and fluoride in reducing the acid solubility of enamel is also disclosed in the Journal of Dental Research (1983) 62 (10) 1049-1053. A further reference discussing the effect of strontium and fluoride is Featherstone, J.D.B. "Remineralization of Artificial Carious Lesions In-vivo and In-vitro", Proceedings Workshop (1983) IRL Press Ltd.
The use of strontium in combination with fluoride in oral compositions is also disclosed in a number of patent references. Included among these references are U.S. Pat. No. 3,888,976, June 10, 1975 to Mlkvys disclosing an effervescent mouthwash tablet containing strontium ions and possibly a fluoride ion source. U.S. Pat. No. 4,367,219, Jan. 4, 1983 to Schole discloses dentifrices containing a combination of strontium EDTA, a ricinoleate salt and a fluoride ion source. U.S. Pat. No. 4,425,549, Nov. 15, 1983 to Shah et al. discloses toothpastes containing a glycyrrhizinate salt, strontium EDTA and a fluoride ion source. Finally European Patent Application No. 0,079,611, June 6, 1983, Shah, discloses oral compositions containing a strontium EDTA complex and a fluoride ion source.
Although there have been a number of approaches disclosed for combatting caculus, there is still the desire and need to develop improved products possessing that property. The prior art while disclosing the use of pyrophosphate salts and polyacrylic acid provides no suggestion to use such materials in a mixture wherein the materials are present in amounts sufficient to achieve the desired level of anticalculus efficacy.
It is an object of the present invention to provide compositions which delivers an anticalculus benefit.
It is a further object of the present invention to produce an effective anticalculus product using a mixture of a pyrophosphate salt and a polyacrylic acid which delivers improved anticalculus performance.
It is still a further object of the present invention to provide anticalculus products which are cosmetically acceptable and do not inhibit remineralization of the teeth.
It is still a further object of the present invention to provide effective methods for combating calculus using the compositions described herein.
These and other objects will become more clear from the detailed description which follows.
All percentages and ratios used herein are by weight unless otherwise specified. Also all measurements referred to herein are made at 25.degree. C. in the composition or on the pure material unless otherwise specified.